[OSM-dev] Extracting national boundaries

Iván Sánchez Ortega ivan at sanchezortega.es
Mon Aug 30 12:26:43 BST 2010

El día Monday 30 August 2010 12:33:51, Colin Smale dijo:
> Current roadblock is that the country relation contains subrelations
> which contain subrelations. I dived a bit deeper into Spain.[...]
> So in order to build up the outer boundary of Spain, I have to query for the 
> boundary of every single town in Spain,

No, you're wrong. You have to EITHER:

- Use the members with "outer"/"inner" roles to build up the multipolygon 
- Use the members with "subarea" roles to build up the multipolygon area

Why is this information duplicated? Don't ask me. If you're really 
data-quality paranoid, then use both the outer/inner and subarea to build up 
two models of the country, then see if they overlap or not.

P.S.: I had a look at Spain admin boundary and fixed up the roles according to 
http://wiki.openstreetmap.org/wiki/Relation:boundary - it still has some 
issues IMHO, but the national-level boundary should be fine.

Iván Sánchez Ortega <ivan at sanchezortega.es>

Un ordenador no es una televisión ni un microondas: es una herramienta 

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